The present invention relates to polymer polyol dispersions, to a process for making them and to polyurethane foams of which one component is such a polymer polyol dispersion. The present invention further relates to a process for preparing polyurethane foams wherein such a polymer polyol dispersion is used as a reaction component.
U.S. Pat. No. 3,789,044 relates to the composition of a polyisocyanate and a hydroxybenzoic acid capped epoxide-containing material. This composition is cured with a tertiary amine to yield durable and flexible coatings or binders.
German Offenlegungsschrift 3 133 103 relates to resins useful for coating compositions. The resins are produced by reacting an epoxy compound having at least two epoxy groups with a monocarboxylic acid having at least one hydroxyl-substituted aromatic radical at a molar ratio of 1:2. The coating composition may contain a cross-linking agent such as a phenol-formaldehyde resin etc. Alternatively, a portion of the hydroxyl groups of the resin may be reacted with a partially blocked polyisocyanate in order to allow internal cross-linking.
British Patent Application 2 059 977 relates to a method for preparing a rigid cross-linked polyurethane foam. In a first step, a flexible foam is produced from
A. either (1) a urethane-containing prepolymer having polyether or polyester backbone segments end-capped with an aromatic isocyanate or (2) an aromatic polyisocyanate and a polyether or polyester polyol; PA1 B. 0.4 to 1,000 moles of water per mole of NCO groups; and PA1 C. an epoxy resin. PA1 A) aromatic polyisocyanates with PA1 B) a mixture containing PA1 C) an organic epoxy resin.
The epoxy resin can be partially modified, for example, by reaction with amines, carboxylic acids, thiols, phenols and alcohols.
After foaming and reshaping, the produced flexible foam is reacted with an epoxy curing agent. Alternatively, components A., B., C. and the epoxy curing agent can be reacted by mixing all components in a one-shot method.
The mentioned British Patent Application teaches that the use of large excesses of water lead to important advantages and improvements over the conventional polyurethane compositions.
The rigidized foam product is said to be useful for fluid filtering such as sewer treatment.
German Offenlegungsschrift 3 621 264 discloses rigid foams containing urethane and isocyanurate groups produced by reacting
2 to 50 weight percent of a tetra- to octafunctional polyether polyol having a hydroxyl number of 150 to 1200, 1 to 80 weight percent of a di- to pentafunctional polyester polyol having a hydroxyl number of 30 to 400, PA2 a blowing agent and a polyisocyanurate catalyst and
It is said that the use of the mixture of the polyether polyols and the special polyester polyols in the particular weight ratio in combination with small amounts of epoxy resins allows reducing the amount of flame retardant agents in the foams. French Patent 1,332,811 (equivalent to U.S. Pat. No. 3,238,273) relates to the production of a polyurethane foam by reacting a polyisocyanate or a polyisothiocyanate with a polyoxyalkylene-polyol in the presence of a modified glycidyl ether. The polyoxyalkylene-polyol preferably is the addition product of propylene oxide and glycerol which is reacted with ethylene oxide. The modified glycidyl ether can be produced by reacting a glycidyl ether, such as the reaction product of epichlorohydrin and glycerol, with a hydroxy-amine at increased temperature.
Unfortunately, none of the above-mentioned references contain any hint how to produce polymer dispersion polyols which are useful for producing polyurethane foams having the desired properties.
British Patent Application 2 146 345 suggests an epoxy-containing polymer polyol derived from an epoxy-containing monomer and a polyol for producing polyurethane resins having high rigidity and improved physical properties such as mechanical strength and heat resistance. The epoxy-containing polymer polyol is produced by polymerizing an unsaturated ester, ether, urethane, amide or acetal containing one or more epoxy radicals via their C.dbd.C double bond. These ethylenically unsaturated monomers can be copolymerized with ethylenically unsaturated nitriles and optionally with other monomers, such as ethylenically unsaturated hydrocarbons, in a polyol. The produced polymer polyol contains a large number of epoxy groups. When producing the polyurethanes, all or a part of the epoxy groups in the produced polymer polyol must be made to bring about ring-opening reaction, such as coupling of epoxy radicals to each other, reaction with an active hydrogen atom-containing compound or reaction with polyisocyanate, in the presence of an epoxy curing agent such as a polyamine, a polycarboxylic acid, an acid anhydride or an organic polyisocyanate. Although British Patent Application 2 146 345 indicates that the epoxy-containing polymer polyol is useful for producing high-resilient and firm, flexible and semi-rigid polyurethane foams, the epoxy-containing polymer polyol is mainly useful for producing noncellular or microcellular elastomers.
It would be desirable to provide new polymer polyols which are particularly useful for producing polyurethane foams.
A process for preparing polymer polyol dispersions by reacting an epoxy compound with an epoxy hardener in the presence of a liquid polyol is known from U.S. Pat. No. 4,305,861. In European Patent Application 0 232 124 it is disclosed that polyurethane foams which have a high flexibility, high resilience and/or high load bearing ability can be produced when using such polymer polyol dispersions. According to the examples of U.S. Pat. No. 4,305,861 the epoxy compound and epoxy hardener are dissolved in the polyol. The mixture is allowed to stand during 24 and 48 hours without stirring in order to allow the polyaddition reaction to take place.
Although this process may be useful on a laboratory scale, unfortunately it has several disadvantages when the polymer polyol dispersion should be produced on a larger scale. Heat is formed during the reaction which is not controllable in a large reactor due to the insufficient heat transfer in an unstirred reaction. Trials to stir the reaction mixture have resulted in flocculation or gelling of the material.
German Offenlegungsschrift 29 43 689 (equivalent to U.S. Pat. No. 4,305,861) relates to polymer polyol dispersions prepared by reacting epoxy resins with epoxy hardeners in the presence of liquid, high molecular weight polyols. The polymer polyol dispersions are said to be useful as clouding agents for plastic materials. Unfortunately, the same problems are faced when producing these polyol polymer dispersions as when producing the dispersions disclosed in European Patent Application 0 232 124.
European Patent Application 0 079 714 discloses phase stable compositions containing a paraffinic polyol chain extender and an isocyanate-reactive prepolymer containing hydroxy and epoxy groups. The prepolymer has been produced by reaction a diepoxide with a monocarboxylic or a dicarboxylic acid such that the prepolymer contains equal amounts of reactable epoxy groups and reactable secondary non-terminal hydroxy groups. The phase stable compositions can be reacted with a polyisocyanate. However, the European Patent Application relates to liquid compositions useful for producing poly(oxazolidone/urethane) thermoset compositions and does not teach how to provide polymer polyol dispersions that are useful for producing polyurethane foams having the desired properties.
Accordingly, one object of the present invention is to produce epoxy-type polymer polyol dispersions in a controllable fashion and substantially without formation of lumps.
One object of the present invention is to provide polymer polyol dispersions which are useful for producing polyurethane foams which have high flexibility, high resiliency and/or high load bearing ability.